Electron mounting structure of a high frequency electron tube



F. J. PILAS March 22, 1966 ELECTRON MOUNTING STRUCTURE OF A HIGH FREQUENCY ELECTRON TUBE Filed April 10, 1961 5 Sheets-Sheet 2 INVENTOR. FRANK J. PILAS March 22, 1966 Filed April 10, 1961 F. J. PILAS ELECTRON MOUNTING STRUCTURE OF A HIGH FREQUENCY ELECTRON TUBE 5 Sheets-Sheet 5 ZZZ 3 4 y i 0 1 I 1 I i 130 l j I 162' 7 7 In I ///x 149 I II I I I I E t 146 4" 7 I I 3 I 3 I /i IN VEN TOR.

FRANK J. PILAS United States Patent 3,242,373 ELECTRON MOUNTING STRUCTURE OF A HIGH FREQUENCY ELECTRON TUBE Frank J. Pilas, Lyndlrurst, N.J., assignor to Radio Corporation of America, a corporation of Delaware Filed Apr. 10, 1961, Ser. No. 101,761 16 Claims. (Cl. 313-450) This invention relates to electron discharge tubes, and particularly to electron tubes of the double-ended type, and to a method of fabricating such tubes.

In certain electron tube applications, such as in the amplification of ultra high frequency electronic signals, it is the practice to use types of electron tubes known as double-ended tubes. These tubes are characterized in that the various electrodes of the tubes are electrically connected with and supported from different portions of the tube envelope, each envelope portion serving as a terminal for its associated electrode. One type of doubleended tube, for example, is a grounded-grid triode wherein the anode is brought out through the top end of the tube, the grid is connected with a side portion of the tube, and the cathode and heater are electrically connected through the bottom end of the tube. The different envelope portions are insulated from one another, and socketing members are provided for making electrical connection to each of the envelope portions.

One advantage of this type of construction is that the capacitive coupling between the tube electrodes is very small. That is, in comparison with single-ended tubes wherein all the electrode connections are brought out through one end of the tube, much larger spacings are provided in the double-ended tubes between the different electrode supporting members. The result of this is that the inter-electrode capacitance of double-ended tubes is much lower than that of single-ended tubes. Also, the double-ended tube permits use of large area electrode supporting members and conductive terminals-having small inductance whereby the total inductance of the electrodes is also much smaller than that of single-ended tubes. Low inter-electrode capacitance and electrode inductances are necessary for efficient performance of electron tubes in ultra high frequency applications, as known, and account for the preference of double-ended tubes over single-ended tubes for these applications.

A problem associated with doubleended tubes, however, is that since the various tube electrodes are supported from difierent parts of the tube envelope, the accuracy of the spacing and positioning of the electrodes within the tubes is dependent upon the dimensional accuracy of the tube envelopes. Thus, in order to provide close control over the spacing and alignment of the tube electrodes, which, as known, are especially critical in tubes used in high frequency applications, it is necessary to fabricate and assemble the envelope parts and the electrode supports to very close tolerances. For this reason, tubes of this type are generally much more expensive than single-ended tube types wherein the spacing and alignment of the electrodes are generally independent of the dimensional variations in the tube envelopes.

A further reason for the large cost of double-ended tubes was the prior art practice of assembling separate sub-asemblies consisting of the individual tube electrodes and the envelope portions to which the electrodes are secured, and then asembling all the sub-assemblies into a complete tube. Such practice requires a number of separate assembling operations which are expensive because of the labor involved. Such practice also requires the use of numerous accurately dimensioned and expensive assembly jigs. Moreover, since the multiple tolerances of all the sub-assemblies may combine to produce large dimensional variations upon assembly of the tube, great 'ice skill and care must be exercised in the assembly of the tube to provide the necessary close tolerance electrode spacings. For this reason, prior art tubes of the doubleended type do not lend themselves to automatic mechanical fabricating means.

Therefore an object of this invention is to provide an improved electron tube structure and method of assembly wherein the problems and expenses encountered in the fabrication of the prior art tubes of the type described are largely avoided.

More particularly, it is an object of this invention to provide an improved tube of the multiple-ended variety wherein a novel and inexpensive method of tube assembly may be used.

Further objects of this invention are to provide an improved tube and method of assembly wherein the accuracy of electrode spacing is largely independent of the dimensional accuracy of the tube envelope and electrode supports; wherein the method of assembly is very simple and readily adaptable to being performed by automatic mechanical means; and wherein the tube electrodes are very accurately positioned and maintained with respect to each other in the finished tube.

An example of an electron tube made in accordance with this invention comprises an envelope including. an open-ended conductive tubular top portion, an insulating intermediate sleeve portion, and a conductive tubular lower portion. The upper end of the top portion is vacuum sealed by a cap member, and the lower portion is vacuum sealed by a ceramic insulating wafer having a number of lead-ins extending therethrough in vacuumtight relation. The tube electrodes include a grid, an anode, and a cathode, the electrodes being mounted in coaxial telescoped relation to each other. The cathode comprises a cathode cup mounted on an open-ended tubular cathode support, and the anode and grid electrodes are in the form of open-ended tubulations.

The anode is supported within the envelope top portion by a washer-like member embracing the anode and secured to an inner step or shoulder provided'within the envelope top portion. The grid is mounted on aflange secured to a second washer-like member secured in turn to the inside Wall of the envelope lower section, and the cathode support sleeve is mounted on a flange supported on the ends of the lead-ins extending through the ceramic wafer. Also provided is a heater which is substantially enclosed within the cathode, the heater being supported by a pair of the lead-ins passing through the ceramic wafer.

During assembly of the tube, all the tube parts except the cap member and cathode cup are assembled in c0ntacting relation within a brazing jig. As will be described hereinafter, the open-ended grid and anode electrodes and cathode support, and the open-ended envelope top portion permit accurate and simultaneous jigging of all the tube elements within a single jig, thereby avoiding the multiple assembling and aligning operations required in the prior art. Also, the means for mounting and securing the electrodes to the various envelope portions permit the use of envelope parts and electrode support members having relatively large dimensional tolerances. Further advantages of this invention with respect to improved means for securing the tube parts together and an improved method of exhausting the tube will also be described hereinafter.

In the drawing:

FIG. 1 is a longitudinal section of an electron tube made according to this invention;

FIG. 2 is a longitudinal section of a brazing jig which may be used for assembling and brazing together certain parts of the tube shown in FIG. 1; and, I

FIG. 3 is a longitudinal section of a brazing jig simi- Patented Mar. 22, 1966 lar to the one shown in FIG. 2 for assembling certain parts of another tube which may be made according to this invention.

The tube As shown in FIG. 1, an improved and novel electron tube which may be fabricated in accordance with this invention and which may be used as a grounded grid triode comprises an envelope 12 including an annular ceramic sleeve member 14 having end surfaces lying in spaced parallel planes normal to the longitudinal axis of the envelope. The bottom portion of the envelope includes a conducting tubular member 16 of metal having an upper axial end 17 sealed to one of the end surfaces of the annular ceramic member 14 and extending away therefrom. The tubular member 16 is provided with a locating shoulder 19 for supporting a ceramic header member 22 during assembly and terminates in a pair of oppositely disposedlongitudinally extending arcuate indexing lugs 24 and 25. The indexing lugs 24 and 25 are provided for facilitating socketing of the electron tube and are of ditferent circumferential extent so that the tube 10 can be received in an accommodating socket in only one annular orientation relative thereto. The ceramic header member 22 is provided with a plurality of bores 28 through which a plurality of electrode support and lead-in conductors 30 extend in vacuum-tight relation.

The other end of the envelope includes an inverted cup-shaped anode top cap 34 of conducting material having a lip or flange 36 at one end sealed to the annular ceramic member 14. A shoulder 37 is provided within the anode top cap 34 connecting the flange 36 to the main body portion for the anode top cap. Also, anode top cap 34 is provided at its other end with an inwardly radially directed lip portion 39, lip 39 defining a circular opening 40 communicating with the interior of the tube 10. For closing opening 40, an anode top cap closure member 42 is provided. Closure member 42 is cup-shaped and has a transverse flange 43 which engages and is vacuum sealed to the inwardly directed lip 39 of the anode cap 34. During exhausting of the electron tube as will be described, closure member 42 is selfaligning within opening 40. Also, for reasons to be described, it is desirable that closure member 42 be relatively small and light weight. To this end, the closure member may also comprise a small circular disk; the disk, however, lacking the self-aligning feature of member 42.

Included within the envelope 12 are a plurality of electrodes including an anode 46, a grid 48 and a cathode 50. Anode 46 and grid 48 are open-ended tubular structures, and cathode 50 comprises an open-ended tubular support sleeve 51 capped by a cathode cup 52 having an electron emissive material coated thereon. Anode 46 is electrically connected to and secured to anode cap 34 by means of a flat washer-like or annular disk member 58. The washer member 58 encircles a portion of the anode and is secured to shoulder 37 of the anode cap. Grid 48 is mounted on a radially extending dish-like flange 60 which is secured to another flat washer-like member 62 secured in turn to the inside wall of the tubular member 16. Flange 60 is provided with a centrally disposed tubular portion 63 which may have an inwardly turned lip 64 for providing balancing and positioning means between the flange and the end of the grid during tube assembly as will be described. Flange 60 is also provided with a transverse lip 66 at its outer edge which contacts the washer-like member 62 adjacent the inner edge 68 thereof. The cathode sleeve 51 is mounted .on a radially extending flange 70 similar to flange 60, flange 70 being supported on three conductors 30 extending into three bores 28 through the ceramic wafer 22. One or more conductors 30 may serve as lead-ins for cathode 50 although for reasons to be described it is desirable to use all three. A coiled heater 72 is provided within the cathode sleeve 51, the ends of the heater being secured to and supported on the ends of two conductors 30 extending through the ceramic water. As will be described hereinafter, all the joints between the envelope parts referred to are made by brazing, copper being the principal brazing material used.

Another example of a tube which may be made according to this invention is shown partially assembled and brazed within a jig 175 in FIG. 3. The tube is a grounded-screen grid tetrode having a control grid 148, a screen grid 149, and an anode assembly including an open-ended anode 146 press fit Within an open-ended anode top cap 34. The remaining tube parts are similar to the corresponding parts of the tube 10.

As known, the most critical inter-electrode capacitance in ultra-high frequency tubes is the capacitance between the anode and the control grid. In both tubes 10 and 110, this capacitance is maintained at a low value due to the large spacing between the anode support members and the grid support members. Moreover, in tube 110, the screen grid flange and flange washer 162 in combination with conductive tubular member 116 electrically connnected thereto, provide very etfective shielding between the control grid flange and the anode assembly 135.

Inductance of the electrodes of tubes 10 and 110 is also maintained at low values. As known, electrode inductance is dependent upon the area of the electrode terminals, the larger the terminal area the smaller the electrode inductance. In tube 10, anode top cap 34 provides a large-area terminal for anode 46; tubular member 16, a large-area terminal for grid 48; and the three conductors 30 combine to produce a relatively large-area terminal for cathode 50. In tube 110, similar large area electrode terminals are provided except that control grid 148 is connected to conductors 130 which pass through the closure water 122.

Although not shown, still further tubes which may be provided in accordance with this invention comprises tubes having additional insulating and conductive tubular portions interposed in end to end relation between the tube top cap and lower tubular conductive member. Such tube constructions permit the use of additional envelope supported electrodes, the number of additional electrodes depending upon the number of extra tubular portions added.

The jig For assembling the tube of FIG. 1, a jig 75 as shown in FIG. 2 is used. The jig 75 comprises an outer generally cylindrical hollow housing 76, The inside wall of jig 75 is formed to provide three tubular coaxial sections 77, 78 and 79, the three sections being adapted for receiving in snug slidable fit therein the anode top cap 34, the ceramic sleeve 14, and the tubular member 16, respectively. A jigging assembly 82 is centrally disposed within the jig and comprises a central post 83, an inner jigging cylinder 84, an inner spacer cylinder 85, an outer jigging cylinder 86, and an outer spacer cylinder 87. The inner and outer jigging cylinders 84 and 86 extend upwardly a predetermined distance beyond the upper ends of the center post 83 and the spacer cylinders 85 and 87 to partially expose the surfaces of the jigging cylinders: for the purpose of receiving tube parts thereon.

As shown in FIG. 2, the jigging assembly 82 is adapted to receive the cathode support sleeve 51, the grid 48 and the anode 46 in a desired spaced relationship. The inner jigging cylinder 84 is of such internal diameter that the cathode support sleeve 51 is snugly received therein. The outer diameters of the inner jigging cylinder 84 and the outer jigging cylinder 86 are such that the grid 48 and the anode 46 are snugly received around the cylinders 84 and 86, respectively. The wall thickness of the inner jigging cylinder 84 thus determines the spacing between the cathode support sleeve 51 and the grid 48 Likewise the wall thicknesses of the outer jigging cylinder 86 and the inner spacer cylinder 85 thus determine the spacing between the grid 48 and the anode 46. The center post 83 and the spacer cylinders 85 and 87 are provided with stepped ends 90, 91, 92 and 93 so as to properly longitudinally locate the anode 46, grid 48, cathode sleeve 51 and the heater coil 72, respectively. The jig 75 is made of a material which is essentially an alloy of aluminum, molybdenum, zirconium and iron, the material being nonwettable by copper.

The method of fabrication Prior to assembly of the tube within the jig 75, several of the tube parts are provided with metallic coatings in order to facilitate brazing of the tube as will be described. The washer-like members 58 and 62, and flanges 60 and 70, all of which are made of steel in this embodiment, are provided with brazing material in the form of a coating of copper of the order of one to three mils thick. The copper coating may be applied by any known methods, although electro-plating has proven most satisfactory for providing the copper on all the surfaces of these parts. The ceramic wafer 22 is metallized about its outer periphery 95 and on the walls of bores 28 with molybdenum. A satisfactory method of providing this metallized coating is to coat the entire wafer with molybdenum by any known metallizing process and then grind off the metallized coating from the flat surfaces of the ceramic. Also, the end surfaces of the annular ceramic portion 14 are first metallized with molybdenum and then provided with a further coating of copper two to three mils thick.

Having thus prepared certain parts of the tube, all the parts thereof excepting the anode top cap closure member 42 and the cathode cup 52 are assembled within the jig 75.

During the assembly of the tube, the jig 75 is oriented with its open end up and the first part to be loaded therein is the anode top cap 34. As shown in FIG. 2, the opening of the anode top cap permits the cap to be inserted within the jig in surrounding relation with the jigging assembly 82. Thereafter, the anode 46 is placed within the jig and around jigging cylinder 86. The anode washer 58 is engaged with the outside of the anode 46 and is allowed to drop downwardly and along the anode until radial portions 97 of the washer engage the shoulder 37 of the anode top cap 34. As will be described hereinafter, it is not necessary that the fit of the anode washer 58 around the anode 46 be very tight since uniform and rigid brazes may be achieved therebetween even with a relatively loose fit. The same is also true with respect to the fit of the anode washer 58 with shoulder 37. Moreover, since the relative positioning of anode 46 with respect to the other tube electrodes is determined solely by the jigging cylinders, neither washer 58 nor top cap 34 perform jigging functions whereby the dimensions of these parts need not 'be held within close dimensional tolerances. In addition, because of the overlapping fit of washer 58 with shoulder 37, the washer is self-aligning with respect thereto.

In tube 110 of FIG. 3 no anode washer is used, the anode 146 being in an interference fit within top cap 134, as described. The relative positioning of the anode 146 with respect to the other tube electrodes of the tube shown in FIG. 3 is thus dependent in a critical way only on the inner and outer diameters of the anode cap 134. The fit of flange 136 of the anode cap 134 with the annular ceramic sleeve 114 is also non-critical since this fit does not affect the orientation of the anode within the jig 175. Therefore, an important feature of this invention is that during the assembly of the tube, the relative positioning of the anode and anode top cap assemblies with respect to the other tube electrodes is determined entirely by a single brazing jig 75 or 175, this relative positioning being independent of the dimensions of the remaining se -42 a;

6 envelope portions and the dimensional inaccuracies thereof.

Subsequent to the loading of the anode 46 and its washer member 58 into the jig 75 of FIG. 2, the ceramic sleeve 14 is dropped into the jig '75 and into engagement with flange 36 of the anode cap 34. Here again neither the dimensions of the ceramic sleeve 14 nor the dimensions of the anode cap flange 36 need to be held tightly since these envelope portions provide no electrode positioning or alignment.

Thereafter the grid 48 and its flange 60 are loaded into the jig, the grid being received snugly around inner jigging cylinder 84. For the purpose of convenience of handling, grid 48 and flange 60 may be preassembled in contacting relation on a transfer quill (not shown) and then inserted into the jig. The fit of the tubular portion 63 of the flange 60 with the grid is relatively snug, and upon removal of the transfer quill from the jig, the grid and flange remain in the jig with the flange resting on the end of the grid. The lip portion 64 within the tubu lar portion 63 of the flange 60 provides balancing and positioning means between the flange and the end of the grid.

Tubular member 16 is then dropped into the jig and into engagement with the other end surface of ceramic sleeve 14. The washer-like member 62 is inserted into the tubular member 16, the outer peripheral edge 202 of the washer 62 engaging the inner wall of tubular mem ber 16. The washer 62 slides inwardly of the tubular member until the washer engages the transverse lip portion 66 of flange 60. It is noted that as with the anode support washer 58 and anode top cap 34, the dimensions of the grid flange 60, grid washer 62, and tubular member 16 need not be held within close tolerances. Positive and self-aligning engagement of washer 62 with flange 60 is assured due to the fla-t overlapping contact of the washer inner portion 201 with lip 66. Also, since the spacing of the grid 48 with respect to the anode 46 and cathode sleeve 51 is determined entirely by jig 75, no jigging functions :are required of flange 60, washer 62, or tubular member 16. Further, as with the fit of the anode washer 58 with the anode 46, the fit of the outer peripheral edge 202 of washer 62 with the inside wall of tubular member 16 need not be accurately controlled. As will be described hereinafter, all that is required for the purpose of adequate brazing is that the edge 202 of washer 62 engage the tubular member wall at several points and that the spacing between other portions of the edge of the washer and the tubular member be not too great.

After placing washer 62, the cathode support sleeve 51 and its flange 70 are loaded into the brazing jig as shown. For convenience of handling, the flange and cathode sleeve may also be preassembled on a transfer quill (not shown). The ceramic wafer 22 is then inserted into the tubular member 16 until it engages the shoulder 19 therein. Prior to this, the heater 72 has been secured to two conductors 30 sealed to and extending through bores 28 of the ceramic wafer. The remaining conductors 30 are then dropped through the bores 28 of the ceramic wafer until they engage the cathode flange 70, as shown.

As mentioned, lugs 24 and 25 are provided for facilitating socketing of the electron tube. Since it is necessary that conductors 30 be engaged within the proper socket conductor contacts for providing the correct circuit conections with the tube electrodes, it is necessary that ceramic wafer 22 and bores 28 therethrough be correctly angularly oriented with respect to lugs 24 and 25. At the time of insertion, ceramic wafer 22 is correctly oriented with respect to lugs 24 and 25 either manually or by mechanical means, not shown, and it is necessary thereafter to prevent rotational movement of the wafer. One simple way of maintaining the wafer orientation is to provide an interference fit between the ceramic Wafer 22 and the tubular member 16. It is known, however, that it is very difficult to fabricate ceramic parts within close tolerances. In order to prevent movement of wafer 22 with tubular member 16, therefore, a brazing ring 205 is placed in an interference fit in with the inside wall of tubular member 16 and snugly against the upper surface of the ceramic wafer 22. The brazing material ring 205 thus serves the dual functions of preventing movement of ceramic wafer 22 and providing a sorce of brazing material for brazing the outer edge 95 of the ceramic wafer to the inside wall of tubular member 16. An alternate arrangement is to coat the outer edge 95 of wafer 22 to a diameter slightly larger than the inside diameter of the tubular member 16. Copper being a relatively soft material permits press fitting of the wafer 22 into tubular member 16. In such case the expense of loading ring 205 is avoided. For brazing the conductors 30 to the ceramic wafer 22 and flange 70, rings 207 of brazing material are provided, as shown.

Having thus assembled the entire electron tube 10 less the anode top cap closure member 42 and the cathode cup 52, the loaded brazing jig 75 is placed in a hydrogen. furnace and heated until the copper brazing material provided on the various tube parts and in the brazing material rings melts and flows to form all the necessary brazed joints.

As mentioned, it is not necessary that exact and closely controlled fits by provided between washers 58 and 52 and the parts to be brazed thereto. The reason for this is that due to capillary action, the molten brazing material having once contacted both parts at a point where the parts touch one another, then flows into and fills up the gaps between the surfaces of the parts which are in adjacent but non-contacting relation. The ability of the brazing material to bridge the space between the parts is determined by the gap size, the surface tension of the brazing material, and the brazing material wettability of the parts. In this embodiment, the washers 58 and 62, and flanges 60 and 70 are made from steel, tubular conductor 16 and anode top cap 34 are made from a nickel-steel alloy, and anode 46 is made from nickel. With a brazing material of copper, it has been found that satisfactory brazed joints between the above parts may be achieved with gaps as large as 2 or 3 mils.

Although several brazing rings 205 and 207 may be used for providing the necessary brazing material during fabrication of tube 10, the use of the copper platings on the tube parts, and especially on the annular ceramic sleeve 14, as described, avoids the necessity of using more brazing rings. The operations of loading these brazing rings into the jig 75 in proper relation to the parts to be brazed involves undesirable extra expense.

The use of the copper plated ceramic sleeve 14 is made possible in accordance with this invention by the use of a jig made from the copper non-wettable alloy. Prior art jigs are generally made from Nichrome. Since Nichrome is wettable by copper it is necessary in the use of Nichrome jigs to prevent the copper from contacting the jig in order to avoid brazing of the tube to the jig. For this reason it has not been feasible in the past to apply the brazing material as a coating on the ends of parts such as the annular ceramic sleeve 14 as in the instant invention, prior art practice instead being to employ accurately dimensioned brazing rings which are carefully located adjacent the parts to be brazed and away from the jig walls. Also, the jigging cylinders of the prior art jigs are of necessity considerably shorter than the electrodes jigged thereby in order to prevent brazing of the electrode supporting flanges to the jigging cylinders. Use of longer jigging cylinders is made possible in accordance with this invention by the use of the non-wettable brazing jigs, the longer jigging cylinders providing more positive and accurate jigging of the electrodes.

After the tube parts have been brazed together, the jig is allowed to cool and the brazed tube removed therefrom. A further advantage of the instant method of assemblyis that because the tube envelope 12 is assembled simultaneously with the tube electrode-s, damage to the fragile electrodes by additional handling is largely avoided. During removal of the tube from the jig, for example, the anode cap 34 is the last-part to leave its jigging section. This prevents tilting or cocking of the tube with respect to the jig 75 until after all the tube electrodes have been lifted from their jigging cylinders. In this manner, dragging of the electrodes against the jigging cylinders and distortion of the electrodes is prevented.

Prior to exhaust and final sealing of the tube 10, cathode cup 52 (FIG. 1) is inserted through the opening 40 of the anode topv cap '34 and positioned on the end of the cathode sleeve 51. Thereafter, the closure member 42 is dropped into the opening 40', the tube 10 being in upright position and the shape of the closure member 42 providing automatic alignment of the closure member within the opening. A ring of brazing material (not shown) is provided between flange 43 and lip 39, or alternately, the closure member is prior coated with a suitable brazing material. The brazing material used to seal the closure member to the anode cap 34 must have a lower melting temperature than copper, and may comprise an alloy of nickel and gold. The reason for this is to prevent softening and loosening of the prior made copper brazes during brazing of the closure member.

The now completed electron tube is placed in an exhausting and heating chamber wherein the metal parts of the tube are degassed, the cathode cup 5-2 sintered to the cathode support sleeve 51, the cathode emissive material activated, and the tube 10 exhausted. The temperature of the chamber is then increased until the nickelgold brazing material melts and vacuum seals the closure member 42 to the anode top cap 34.

Still further advantages of this invention may best be realized by a comparison with the prior art fabrication of a tube similar to the tubes shown in FIGS. 1 and 3. The method of fabrication of such prior art tube, for example, is to separately assemble and braze together one sub-assembly comprising a mount including a ceramic closure wafer and all the electrodes supported thereon, and a second sub-assembly comprising an envelope including a tubular conductive member, a ceramic insulating sleeve, and a closed-ended anode assembly similar to the anode assembly of the tube shown in FIG. 3. The two sub-assemblies are then assembled into a complete tube by inserting the mount into the envelope, the mount being coaxial with the envelope, and the ceramic closure wafer abutting against and resting on an internal shoulder within the tubular conductive member. Thereafter, the tube is exhausted, the tube gases being exhausted from within the tube through the space between the ceramic closure wafer and the tubular conductive member. After exhaust, the ceramic Wafer is vacuum sealed to the tubular conductive member.

One problem with this prior art method is that because of the relatively heavy weight of the mount subassembly and the pressure of the closure Wafer against the internal shoulder, the exhaust path between the wafer and the shoulder is often restricted or closed-up, such restriction preventing efiicient and proper tube exhausting. To improve this situation, louvers or indentations are formed in the tubular conductive member to provide exhaust ports between the ceramic closure wafer and the conductive member. It has been found, however, that formation of such louvers and indents by conventional punch means often produces tiny cracks or tears in the metal of the conductive member which result in air tubes. Moreover, it has been found somewhat difficult to adequately fill up the exhaust ports with brazing material after exhausting to vacuum seal the ports.

A still further problem of this prior art assembly method is that the only means available for orienting the mount with the envelope and providing correct anode spacing with respect to the mount electrodes is the engagement of the ceramic wafer with the internal shoulder of the conductive tubular member. Since the anode is supported from the anode top cap at the other end of the envelope, the dimensions of all the intermediate envelope portions along with the positioning of the mount electrodes with respect to the ceramic wafer must be held within close dimensional accuracy. As mentioned, it is diflicult to fabricate ceramic members within close dimensions, and it is further undesirable for reasons of economy to have to provide close dimensional control over the other envelope portions.

In accordance with this invention, however, these problems are completely avoided. Since exhaust takes place through the anode top cap 34, the ceramic closure wafer 22 is sealed to the tubular portion 16 prior to exhaust and no exhaust ports therebetween need be provided. The small size and lightness of weight of the closure cap 42 obviates the need for special exhaust ports. Also, even if such ports were required, the small size of the closure cap 42 in comparison with the size of the ceramic wafer requires the use of much less brazing material, joints requiring large amounts of brazing material being somewhat diflicult to form, as known.

Further, because of the open-ended tubular tube parts, as provided by this invention, almost the entire tube may be assembled at one time in one jig. The advantage of this, as described, is that the relative spacing and alignment of the tube electrodes is determined almost entirely by the single jig, the dimensional tolerances of the envelope portions having little effect thereon. Also, because of the ease with which the tube parts may be loaded into the jig, and the self-aligning features thereof, it is apparent that the method of assembly of this invention readily lends itself to be performed by automatic mechanical means.

Still further advantages are provided by the method of assembling and brazing in accordance with this invention, such advantages, it being noted, even having utility in the fabrication of single-ended tubes. One such advantage, for example, is that it has been found more economically feasible to provide strong and reliable joints of ceramic wafers to conductive tubular members by the method of this invention than in the prior art tube described. The reason for this is that since the mount and ceramic wafer to envelope brazes are made simultaneously, it is possible to use copper brazing material for all the joints. Copper is an inexpensive and satisfactory brazing material for brazing together the various mount parts, and moreover, is the most satisfactory presently known brazing material for brazing ceramic to metal. In prior art practice wherein the metal envelope is brazed to the ceramic wafer after mount brazing, it is the practice to use copper for the mount joints and some other lower temperature melting material for the ceramic Wafer to conductive member joint. With presently available brazing materials, not only is the joint made with such other material less satisfactory than joints made with copper, but the use of practically all other brazing materials is more expensive than copper.

A still further advantage is that since the envelope is firmly secured to the ceramic wafer prior to exhausting, it is possible to exhaust the tube in an upright position. Prior art practice requires that the tubes be exhausted in inverted position to prevent the mount from falling out of the envelope. The significance of this is that the cathode cup 52 may be placed on the end of the cathode sleeve 51 in loose contacting relation as compared with the snug fitting relation required in the prior art. The disadvantage of the snug fit is that it places a lower limit on the thickness of the cathode sleeve wall, a thinner wall not providing suflicient mechanical strength for receiving the cathode cup 52 in the necessary tight fit. For reasons relating to efficient tube operation, it has been found that in certain instances it is desirable to use extremely thinwalled cathode supports. By permitting upright exhaust 1f) and hence loose fit of the cathode cup to the cathode sleeve, the wall thickness of the tubes of the present invention may be reduced to a greater extent than possible in the prior art.

What is claimed is:

1. An electron discharge device comprising an envelope including a conductive tubular portion and a ceramic closure member sealing one end of said tubular portion, a plurality of lead-ins extending through said closure member in vacuum-tight relation therewith, a plurality of tubular electrodes within said envelope, a first flange secured to one end of one electrode and mounted on the ends of said lead-ins within said envelope, a second flange secured to one end of another of said electrodes and having a transverse lip, and an annular disk secured to said lip adjacent the inner edge of said disk, and said disk being secured at its outer peripheral edge to the inside of the tubular portion of said envelope.

2. An electron discharge device comprising an envelope including a conductive tubular portion and a ceramic closure member sealing one end of said tubular portion, a plurality of lead-ins extending through said closure member in vacuum-tight relation therewith, a plurality of open-ended tubular electrodes Within said envelope, said electrodes being coaxial and in telescoped relation to one another, a first flange secured to one endof one electrode and being mounted on the ends of said lead-ins within said envelope, a second flange secured to one end of another of said electrodes, said second flange having a generally conical shape and having a transverse flange at one end thereof, and an annular disk secured to said lip adjacent the inner edge of said disk, and said disk being secured at its outer peripheral edge to the inside of said tubular portion.

3. An electron discharge device comprising an envelope including a conductive tubular portion having oppositely disposed socketing terminals extending longitudinally from one end thereof, a ceramic closure member sealing one end of said tubular portion adjacent said terminals, a plurality of conductors extending through said closure member in vacuum-tight relation therewith, a plurality of tubular electrodes coaxially mounted within said envelope, one of said plurality of electrodes comprising a grid, a first flange secured to one end of one of said electrodes, said flange being connected adjacent its periphery to said conductors, a second flange secured to one end of said grid, said second flange having a transverse lip, an annular disc secured coaxially to said second flange by means of said lip being fixed to said disc adjacent the inner edge of said disc, said disc being secured at its outer peripheral edge to the inside of the tubular portion of said envelope.

4. An electron discharge device comprising an envelope including a conductive tubular portion having oppositely disposed socketing terminals extending longitudinally from one end thereof, a ceramic closure member sealing one end of said tubular portion adjacent said terminals, a plurality of conductors extending through said closure member in vacuum-tight relation therewith, a plurality of tubular electrodes coaxially mounted within said envelope, one of said plurality of electrodes comprising a grid, a first flange secured to one end of one of said electrodes, said flange being connected adjacent its periphery to said conductors, a second flange secured to one end of said grid, said second flange having a transverse lip, an annular disc secured to said second flange, said lip being fixed to said disc adjacent the inner edge of said disc, said disc being secured at its outer peripheral edge to the inside of the tubular portion of said envelope, said terninals providing means for electrically grounding said gri 5. An electron discharge device having an envelope including a top envelope assembly, said assembly comprising an open-ended tubular member having an annular outwardly directed shoulder therein, a cap member vacuum sealing one end of said tubular member, a tubular anode mounted coaxially within said tubular member, and an annular disk member, the inner edge of said disk member embracing and being secured to a peripheral portion of said anode, and said disk member being secured at a peripheral portion thereof to said shoulder.

6. An electron discharge device having an envelope including a top envelope assembly, said assembly comprising an open-ended tubular member having an inwardly directed lip at one end and an annular outwardly directed shoulder adjacent the other end, said lip defining an opening, a cap member vacuum sealed to said lip for closing said opening, a tubular anode, and an annular disk member supporting said anode coaxially within said tubular member, the inner edge of said disk member embracing and being secured to a peripheral portion of said anode, peripheral portions of said disk member being in overlapped relation with, and secured to, said shoulder.

7. An electron discharge device comprising an envelope including a ceramic sleeve, an anode cap, and an anode cap closure member, a cylindrical anode within said envelope, said anode cap comprising a tubular portion having an inwardly directed lip at one end, and an annular collar portion at the other end, said lip defining an opening into said envelope, and said collar portion comprising a radially extending shoulder portion and a longitudinally extending flange portion, the end of said flange portion being sealed to one end of said ceramic sleeve, said closure member being cup-shaped and having a transverse flange sealed vacuum tight to said lip, and an annular disk member engaging a peripheral portion of said anode, peripheral portions of said disk being secured to said shoulder portion for supporting said anode coaxially within said anode cap.

8. An electron discharge device having an envelope including a tubular ceramic member, a tubular conductive member sealed at one end to one end of said ceramic member, an open-ended tubular anode cap, and an anode cap closure member, said anode cap being provided with an outwardly extending annular shoulder at one end having a flange at the periphery thereof, said flange extending parallel to the longitudinal axis of said anode cap and being sealed to the other end of said ceramic member, and a plurality of tubular electrodes mounted coaxially and in telescoped relation within said envelope, a flange secured to one end of one of said electrodes, said flange having a transverse lip, and an annular disk member secured to said lip, the peripheral edge of said disk member being secured to the inside wall of said tubular conductive member.

9. An electron discharge device having an envelope including a tubular ceramic member, a tubular conductive member sealed at one end to one end of said ceramic member, a tubular anode cap, and an anode cap closure member, said anode cap being provided with an inwardly turned lip portion at one end, an outwardly extending annular shoulder at its other end, and a flange at the periphery of said shoulder, said flange extending parallel to the longitudinal axis of said anode cap and being sealed to the other end of said ceramic member, said closure member being cup-like and having a transverse flange vacuum sealed to said lip portion of said anode cap, and a plurality of tubular electrodes mounted coaxially and in telescoped relation within said envelope, a flange secured to one end of one of said electrodes, said flange having a transverse lip, and an annular disk member secured to said lip, the peripheral edge of said disk member being secured to the inside wall of said tubular conductive member.

10. An electron discharge device having an envelope periphery of said shoulder, said flange extending parallel to the longitudinal axis of said anode cap and being sealed to the other end of said ceramic member, said closure member being cup-like and having a transverse flange vacuum sealed to said lip portion of said anode cap, and a plurality of tubular electrodes mounted coaxially and in telescoped relation within said envelope including an anode and a grid, a washerencircling and being secured to the outside of said anode, peripheral portions of said washer being in overlapped relation with and secured to said shoulder of said anode cap for supporting said anode therein, a radially extending flange secured to one end of said grid, said flange having a transverse lip and an annular disk member secured to said lip, the outer peripheral edge of said disk member being secured to the inside wall of said tubular conductive member, and portions of said disk member adjacent the inner edge thereof being in overlapped relation with said lip.

11. An electron discharge device comprising an envelope including a first conductive tubular portion, a second conductive tubular portion and a ceramic tubular portion interposed between said first and second conductive tubular portions, said first conductive tubular portion having oppositely disposed arcuate shaped terminals extending longitudinally from one end thereof, a ceramic closure member sealing one end of said first tubular portion adjacent said terminals, a plurality of conductors extending through said closure member in vacuum-tight relation therewith, a plurality of tubular electrodes coaxially mounted within said envelope, one of said plurality of electrodes comprising a grid, and another of said electrodes comprising an anode, a first flange secured to one end of one of said electrodes, said flange being connected to said conductors adjacent its periphery, a second flange secured to one end of said grid, said second flange having a transverse lip, an annular disc secured coaxially to said second flange, said lip being fixed to said disc adjacent the inner edge of said disc, said disc being secured at its outer peripheral ege to the inside of said first tubular portion of said envelope, said anode being supported from said second conductive tubular member, and said terminals providing means for electrically grounding said grid.

'1 2. An electron discharge device comprising a closed envelope, .a plurality of electrodes including a tubular anode mounted with said envelope, said envelope including an outwardly extending shoulder, an annular disk member disposed around and secured to the outer wall of said anode, and radially outer portions of said disk member being in overlapped relation with and secured to said shoulder thereby supporting said anode coaxially within said envelope and in fixed relation with another of said electrodes.

:13. An electron discharge device comprising an envelope including a first tubular conductive member, an insulating sleeve member, and a second tubular conductive member, said sleeve member being disposed between said first and second conductive members, and a pair of tubular coaxial electrodes within said envelope secured one each to each of saidenvelope conductive members, said one conductive member having an outwardly extending shoulder, a washer encircling and secured to the outside wall of the outer one of said electrodes, radially outer portions of said washer being in overlapped relation with and secured to said shoulder, a radially outwardly extending flange secured to the end of the other of said electrodes, and an annular disk, radially outer portions of said flange and radially inner portions of said disk being overlapped and secured together, and said disk being secured at its outer edge to the inside of said second conductive member.

14. An electron discharge device having an envelope including a tubular ceramic member, a first t-u-bular conductive member sealed at one end to an end of said ceramic member, a second tubular conductive member,

and a closure member closing one end of said second conductive member, said second member being provided with an outwardly extending annular shoulder near its other end, said shoulder having a peripheral flange sealed to the other end of said ceramic member, and a pair of tubular electrodes mounted coaxially and in telescoped relation Within said envelope, a washer encircling and being secured to the outside of one of said electrodes, peripheral portions of said washer being in overlapped relation with and secured to said shoulder of said second member, a radially extending flange secured to one end of the other of said electrodes, said flange having a transverse lip, and an annular disk member secured to said li-p, the outer peripheral edge of saiddisk member being secured to the inside wall of said first tubular conductive member, and portions of said disk member adjacent the inner edge thereof being in overlapped relation with said lip.

15. An electron discharge device having an envelope including a tubular ceramic member, a tubular conductive member sealed at one end to an end of said ceramic member, an open-ended tubular anode supporting memher, and a closure member closing one end of said anode supporting member, said anode supporting member being provided with an outwardly extending annular shoulder near its other end, said shoulder having a peripheral flange extending parallel to the longitudinal axis of said anode supporting member and being sealed to the other end of said ceramic member, and a plurality of tubular electrode-s mounted coaxially and in telescoped relation Within said envelope including an anode, a cathode, and a grid, a washer encircling and being secured to the outside of said anode, peripheral portions of said washer being in overlapped relation with and secured to said shoulder of said anode supporting member for supporting said anode therein, a radially extending flange secured to one end of said grid, said flange having a transverse lip, and an annular disk member secured to said lip, the outer peripheral edge of said disk member being secured to the inside wall of said tubular conductive member, and portions of said disk member adjacent the inner edge thereof being in overlapped relation with said lip.

16. An electron discharge device having an envelope including a tubular ceramic member, a tubular conductive member sealed at one end to an end of said ceramic member, a first closure member sealing the other end of said conductive member, a plurality of conductors extending through said first closure member in vacuum tight relation therewith, an open-ended tubular anode supporting member, and a second closure member closing one end of said anode supporting member, said anode supporting member being provided with an outwardly extending annular shoulder near its other end, said shoulder having a peripheral flange extending parallel to the longitudinal axis of said anode supporting member and being sealed to the other end of said ceramic member, a pinrality of tubular electrodes mounted coaxially and in telescoped relation within said envelope including an anode, a cathode, and a grid, a washer encircling and being secured to the outside of said anode, peripheral portions of said washer being in overlapped relation with and secured to said shoulder of said anode supporting member for supporting said anode therein, a radially extending first flange secured to one end of said grid, said first flange having a transverse lip, and an annular disk member secured to said lip, the outer peripheral edge of said disk member being secured to the inside wall of said tubular conductive member, and portions of said disk member adjacent the inner edge thereof being in overlapped relation with said lip, and a radially extending second flange secured to one end of said cathode electrode, said second flange being mounted on said conductors.

References Cited by the Examiner UNITED STATES PATENTS 1,687,505 10/1928 Nolte 313-247 2,217,418 10/1940 Rabuteau 313247 X 2,438,899 4/1948 Chevigny et al. 313-346 2,439,641 4/1948 Wheeler 313-293 2,752,532 6/1956 Dussaussoy et al. 316--19 2,792,271 5/1957 Beggs 316-19 2,794,933 6/1957 Song et a1. 313-249 2,957,997 10/1960 Manfredi 313249 X 2,962,619 11/1960 Rose 313-246 GEORGE N. WES'TBY, Primary Examiner.

RALPH G. NILSON, Examiner.

C. R. CAMPBELL, J. E. BECK, Assistant Examiners. 

16. AN ELECTRON DISCHARGE DEVICE HAVING AN ENVELOPE INCLUDING A TUBULAR CERAMIC MEMBER, A TUBULAR CONDUCTIVE MEMBER SEALED AT ONE END TO AN END OF SAID CERAMIC MEMBER, A FIRST CLOSURE MEMBER SEALING THE OTHER END OF SAID CONDUCTIVE MEMBER, A PLURALITY OF CONDUCTORS EXTENDING THROUGH SAID FIRST CLOSURE MEMBER IN VACUUM TIGHT RELATION THEREWITH, AN OPEN-ENDED TUBULAR ANODE SUPPORTING MEMBER, AND A SECOND CLOSURE MEMBER CLOSING ONE END OF SAID ANODE SUPPORTING MEMBER, SAID ANODE SUPPORTING MEMBER BEING PROVIDED WITH AN OUTWARDLY EXTENDING ANNULAR SHOULDER NEAR ITS OTHER END, SAID SHOULDER HAVING A PERIPHERAL FLANGE EXTENDING PARELLEL TO THE LONGITUDINAL AXIS OF SAID ANODE SUPPORTING MEMBER AND BEING SEALED TO THE OTHER END OF SAID CERAMIC MEMBER, A PLURALITY OF TUBLUAR ELECTRODES MOUNTED COAXIALLY AND IN TELESCOPED RELATION WITHIN SAID ENVELOPE INCLUDING AN ANODE, A CATHODE, AND A GRID, A WASHER ENCIRCLING AND BEING SECURED TO THE OUTSIDE OF SAID ANODE, PERIPHERAL PORTIONS OF SAID WASHER BEING IN OVERLAPPED RELATION WITH AND SECURED TO SAID SHOULDER OF SAID ANODE SUPPORTING MEMBER FOR SUPPORTING SAID ANODE THEREIN, A RADIALLY EXTENDING FIRST FLANGE SECURED TO ONE OF END OF SAID GRID, SAID FIRST FLANGE HAVING A TRANSVERSE LIP, AND AN ANNULAR DISK 